How to round all the elements of a matrix with numpy in python ?

The SciPy library provides a convenient way to round all the elements of a matrix with numpy in python. Using numpy.around will allow us to set the number of decimal places and rounding type for each element in the array. Examples

Create a matrix of float with numpy

Let's create first a matrix of float with numpy

import numpy as np

np.random.seed(42)

data = np.random.rand(4,5) * 100.0

Output

array([[37.45401188, 95.07143064, 73.19939418, 59.86584842, 15.60186404],
       [15.59945203,  5.80836122, 86.61761458, 60.11150117, 70.80725778],
       [ 2.05844943, 96.99098522, 83.24426408, 21.23391107, 18.18249672],
       [18.34045099, 30.4242243 , 52.47564316, 43.19450186, 29.12291402]])

Round all elements of a matrix with numpy

For example, if you wanted to round all numbers in a matrix to two decimal places, you would use np.around(matrix, decimals=2). You can also use numpy.floor or numpy.ceil to round numbers down or up respectively. Additionally, if you want to round all elements of a matrix element-wise, you can use the np.round function, which provides more control over how the rounding is performed:

np.around(data,2)

Output

array([[37.45, 95.07, 73.2 , 59.87, 15.6 ],
       [15.6 ,  5.81, 86.62, 60.11, 70.81],
       [ 2.06, 96.99, 83.24, 21.23, 18.18],
       [18.34, 30.42, 52.48, 43.19, 29.12]])

Example round with 1 decimals:

np.around(data,1)

Output

array([[37.5, 95.1, 73.2, 59.9, 15.6],
       [15.6,  5.8, 86.6, 60.1, 70.8],
       [ 2.1, 97. , 83.2, 21.2, 18.2],
       [18.3, 30.4, 52.5, 43.2, 29.1]])

Example round with 0 decimals:

np.around(data,0)

Output

array([[37., 95., 73., 60., 16.],
      [16.,  6., 87., 60., 71.],
      [ 2., 97., 83., 21., 18.],
       [18., 30., 52., 43., 29.]])

Numpy round() vs around()

Same functions

np.round(data,2)

Output

array([[37.45, 95.07, 73.2 , 59.87, 15.6 ],
       [15.6 ,  5.81, 86.62, 60.11, 70.81],
       [ 2.06, 96.99, 83.24, 21.23, 18.18],
       [18.34, 30.42, 52.48, 43.19, 29.12]])

Convert a matrix of floats into integers

Another solution is to convert the matrix of floats to integers with astype(int):

data.astype(int)

Output

array([[ 0, 62, 50, 57, 11],
       [57, 19,  7, 10, 90],
       [62, 42, 58, 91, 26],
       [ 6, 76, 71, 56, 79]])

References